I just watched an interesting little video on the BBC website.
A study took two identical twins (therefore genetically identical) who are both already fit 'adventure athletes' and gave them different diets for 12 weeks. One turned vegan and the other continued to eat meat and dairy.
The point is to see if a vegan diet was more or less healthy than someone who eats meat.
The video is only 7 minutes and kind of interesting, but if you just want to skip to the conclusion at the end….
There was virtually no difference at all.